ChemInform Abstract: Preparation of Ceph‐3‐em Esters Unaccompanied by Δ³ to Δ² Isomerization of the Cephalosporin Derivatives.

Abstract

Preparation of Ceph-3-em Esters Unaccompanied by ∆ 3 to ∆ 2 Isomerization of the Cephalosporin Derivatives. -Optimized conditions are found for the exclucive formation of ∆ 3 -cephem esters of type (III) from free acids (I) with alkyl chlorides (II). No ∆ 3 to ∆ 2 isomerizations occur by treatment of the acids with an equimolar mixture of cesium and potassium carbonate in 5:3 DMF/dioxane followed by addition of the chloride.